The present invention relates generally to vehicle suspension systems and, in an embodiment described herein, more particularly provides a trunnion air suspension system.
Trunnion suspension systems are used for transporting very heavy loads, since they distribute a load among a larger number of sets of wheels/tires than other suspension systems, and axles separately connected to frame rails can move independently of each other in a trunnion suspension system. In general, a conventional trunnion suspension system includes an axle attached to each frame rail, with two wheel/tire sets mounted to each axle. One wheel/tire set is mounted inboard of the frame rail, and the other wheel/tire set is mounted outboard of the frame rail, on each axle.
An example of a trunnion suspension system is described in U.S. Pat. No. 3,406,980, the entire disclosure of which is incorporated herein by this reference.
In order to increase load carrying capacity, multiple trunnion suspension systems are typically stacked longitudinally along the frame rails. Thus, it is very desirable for a trunnion suspension system to be longitudinally compact, so that multiple suspension systems can be accommodated conveniently along the frame rails as needed to support and distribute the required load.
There is also a need for trunnion suspension systems to be laterally compact, since the suspension systems must traverse public roadways which are limited in width. For this reason, the sets of wheels mounted on each axle are typically spaced close together straddling the frame rail, with very little space between the wheel sets. This has created a problem for mounting brake chambers or brake actuators between the wheel sets.
Some manufacturers have attempted to solve this problem by mounting only one brake actuator between the wheel sets. Unfortunately, in some instances a single brake actuator does not provide sufficient force to generate enough braking, particularly when very large loads are being transported. Other manufacturers have mounted multiple brake actuators to the trunnion beam behind the wheel sets. However, when the axle rotates relative to the trunnion beam, the brake actuators do not rotate, and so a brake actuator rod extending between a brake actuator and a brake camshaft is twisted, which leads to improper operation of, and possible damage to, the brakes.
There is also a need for trunnion suspension systems to be more conveniently serviced. In typical trunnion suspension systems, a hub and drum must be removed prior to removing a brake slack adjuster arm. This increases the cost of maintaining such suspension systems.
Thus, it may be seen that improvements are needed in the art of trunnion suspension systems. It is an object of the present invention to provide such improvements.